Wire matrix print head

ABSTRACT

A wire matrix print head comprised of a plurality of impact print wires or styli, each having an input end for receiving an impact and an output end for delivering an impact to a record medium through an inking ribbon. The impact end of said wires or styli are arranged in a specialized elliptical format while the output end of the wire styli are formed into a planar straight line configuration, thus providing for a minimal amount of bending arc along the length of the styli. This configuration permits direct transmission of the impact forces to the output end and permits each stylus to be of equal length to the other styli. Efficacious provision is made for adjusting the stroke length of each stylus even though a uniform electromagnet for each stylus is used to provide the activating or impact impulse.

This is a continuation of U.S. application Ser. No. 354,574, filed Apr.26, 1973, now abandoned.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

This invention relates to a high-speed printer of the matrix typewherein a plurality of thin wire styli are selectively impacted in orderto deliver an impact to a record medium.

In the present day use of high-speed output devices, such as result fromelectronic calculators, computing machines, and data processingequipment, it is necessary to print output information very rapidlyclearly, efficiently, and often with the capability of producingmultiple instantaneous copies.

In such a printer with mechanical elements, the inertia of themechanical elements is a factor which may limit the speed of operation.In such high-speed use of matrix printers having a plurality of styliwires to form dots which can be printed so as to form characterconfigurations, the low masses of the wire styli and the actuatingmechanisms permit the accomplishment of very high-speed operation,especially since each wire stylus need only travel a very short stroketo make its impression on the record medium.

The printer of the present invention is that type which has the styliwires so arranged at its output end so as to form a straight line whichcan be moved across a record medium rapidly to print and form characterson the record medium. Each character printed would be formed by asequence of successive wire impacts on the moving medium.

In the prior art, a variety of wire dot matrix printers have beendeveloped having various types of elements and configurations. Some ofthese printers have a single drive or actuating means which is used toselectively actuate one or more of the wire styli. Other forms of suchmatrix printers have a plurality of actuating means for activation ofvarious of the wire styli. Among the problems involved therein is thephysical space problem wherein the actuating means for each of thevarious styli require that the styli be widely spaced at the end whereinthe styli receive their actuation and at the same time, at the otherend, the styli tips (which deliver the impact to the record medium) mustbe brought into a very small aligned spacial configuration. This hasgenerally required, in the prior art, that each of the styli must berather sharply bent from a wide separation at one end to a closealignment at the other end with the result that certain styli must be oflonger length than others and other styli must be of shorter length thanothers. The various lengths and various difference in masses involved inthe styli and the various amount of arcing or bending along the lengthof the styli present problems which must be overcome by complex guidemeans and complex driving or actuation means wherein each stylus must becompensated for the amount of energy impact it receives, the length ofthe stroke of the activating means which hammers it and the mass andacceleration of the hammer which delivers the impact to the stylus.

Among other problems that arise in the use of the wire styli forprinting at high speeds, is the factor of rapid return to "home"position of each stylus without excessive bouncing, vibration, orovershoot. This generally has been accomplished in the prior art bymeans of spring bias means.

Other factors and problems involved in the prior art in regard to suchwire stylus dot printers involve the delivering of sufficientacceleration and velocity to each individual wire stylus in order toresult in sufficient impact at the printing end of the stylus to printrapidly and clearly on one or on several underlying recording media, andwith sufficient rapidity of return to home position to enable quickavailability for the next impact cycle. Thus, the diminution of massboth of the wire stylus and of the actuating or impact means has been aproblem of considerable importance in addition to developing rapid yetsimple means for selectively actuating each of any of the individualstyli both separately and/or simultaneously.

SUMMARY OF THE INVENTION

In accordance with the subject invention, there is obtained a high-speedmatrix dot printer by utilizing a plurality of wire styli which aregrouped at one end (output end) as a straight line in a plane and at theopposite end are formed along the periphery of an elliptical plane. Eachindividual stylus is spring biased to its "home" position and is fixedlyattached to a nylon impact button which is subject to an impact from anarmature of an electromagnet. A plurality of uniformly constructedelectromagnets are provided, each of which has an armature having ahammer or impact end such that one electromagnet and armature-hammer isprovided for each wire stylus. Each of the uniform electromagnets has anarmature which is held by a specialized armature retainer, whicharmature retainer provides for simple adjustment of the position andstroke length of the structure. The armature retainer also providesspring bias means for positioning the armature in its nonenergizedposition.

Due to the specialized elliptical positioning of the impact receivingends of the wire styli, the elongated length of each of the styli are ofequal length to each other and have only a minimal amount of arc or bendalong the elongation of the wire stylus, this bending being equal to orless than one wire diameter (0.014 inch). This permits directtransmission of impact from one end of the stylus to the other, andfurther there is no need for making separate and different adjustmentsin the strokes of the various armatures to compensate for differences inlength, mass, or angle of bend of the various wire styli.

The printer of the subject invention is capable of greater than 1,000imprints per second per individual stylus.

Further, due to the simplicity of the wire styli in 30 that they are ofequal length, equal mass, and minimally bent, and since there are novariations in impact energy or stroke differences involved between thevarious styli, each of the activating electromagnets and armatureassemblies can be made uniform in nature so that considerable economy inparts, assembly, and maintenance are provided both in terms ofsimplicity and cost.

Further, an armature retainer is provided with an elastomeric bumpercushion adjacent and opposite the impact side of the armature which thusacts as a bumper-cushion to dampen any excessive vibration resultingfrom the de-energization of the electromagnets and from the return cycleof the armature and of the spring biased wire stylus after itsimpact-print cycle is completed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric and schematic representation of the wire matrixprint head showing the major components in cooperative relationship.

FIG. 2 is a plan view (looking from the top) of the wire matrix printhead showing an arrangement of nine electromagnetic armatures used ashammers to drive the wire styli (which print against a ribbon on paperat the output end).

FIG. 3 shows a side view of a cutout (3--3 of FIG. 2) of the wire matrixprint head illustrating how the armature contacts the impact head todrive the stylus wire which is supported by the wire guide assembly.

FIG. 4A is a perspective schematic view of the wire guide assemblyshowing the wire styli being supported at the output end for printing onpaper through ribbon while the input end of each stylus is broughtthrough a circular cylindrical portion having apertured extensions onthe planar surface of the cylindrical head and on which the locus of thepin hole supports are formed in an ellipse.

FIG. 4B shows a plan or top view of the cylindrical block of the wireguide assembly, including the raised stylus holes used to support thestylus wires which are arranged in elliptical configuration.

FIG. 4C shows an enlarged view of the circular plane of the topcylindrical extension of the wire guide assembly, from a plan or topview, and illustrates in schematic form how the pin hole supports forthe wire styli are located to form a locus of points equally spacedalong the periphery of an ellipse.

FIG. 5 is a graph of wire stylus motion against time (in microseconds)to illustrate wire flight and impact cycles for different thicknesses ofrecord medium.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 there is seen a side or elevation view of a simplifiedschematic drawing of the wire matrix print head. Only the essentialelements are shown for clarity while the manifold and other elements areshown in other drawings.

A metal mounting plate 6 is shown supporting a stylus wire guideassembly 1 and also a series of electromagnetic armatures 9 in a generalconfiguration which surround the central portion of the wire guideassembly 1, especially the area designated 21 which is the upper portionof the wire guide assembly and which may be designated as a circularcylindrical block through which the stylus wires (such as 13a, 13b, 13c,etc.) pass and which terminate in a head or impact button 8 locatedproximately to an armature 9.

It will be seen that relative downward motion of the magnetic armature 9will operate so as to strike the impact head or button 8 in order todrive into motion a wire stylus such as 13, which at the "output end"18, will extend beyond the base of the wire quide assembly in order topress against a ribbon and paper in order to imprint a dot mark (seeFIG. 4A). After the finish of the hammer impact of armature 9 againstthe impact button 8, then the compression or return spring 7 will causethe stylus to return upward into its normal or home position.

Referring to FIG. 1 and FIG. 3, the armature 9 is held in anelectromagnet assembly in which a magnetic core 16 which defines acenter pole of the electromagnet and which is surrounded by a coil 19 ina general configuration about the cylindrical block extension 21. A nut17 holds the magnetic core 16 to the mounting plate 6 in addition tosecuring the magnetic yoke 15 which bends from the base up around theside of the magnetic core 16 and defines an outer pole of theelectromagnet.

Adjustably attached to the magnetic yoke 15 is an armature retainer 10having a central portion overlying the stylus engaging end of thearmature and an arm extending radially outward from the central portionbeyond the outer pole for applying a moment of force to the armaturetending to cause the stylus engaging end to rotate about the outer poletoward the central position which holds or retains the magnetic armature9 in close proximity to the top of the magnetic core 16.

A loading spring 11 ensures that the outer end of the armature 9 will bemaintained in close proximity to the top of yoke 15 in order to maintaina continuous circuit for magnetic flux. At the inside or hammer end ofthe armature retainer 10, there is provided a backstop or bumper cushion20 which cushions the return shock of the armature back against theretainer 10.

The actual stroke or motion distance accomplished by the armature 9 inits hammer-like action against the stylus impact button head 8 isdetermined by adjusting the height of the armature retainer 10 by meansof screw 12 and a mounting clamp 14.

In FIG. 2, there is shown a plan or top view of a wire matrix print headshowing a series of 9 magnetic armatures (hammers) placed in aconfiguration about the circular cylindrical block 21. Each armature 9covers the impact button head 8 of the individual wire styli which maybe actuated into motion underneath the armature tip 9.

The entire assembly of the nine electromagnets and armatures issupported on the mounting plate 6 and one particular electromagnet isshown in greater detail in order to illustrate what lies underneath. Aswill be seen by the broken lines, there rests a core 16 underneath eachof the armature retainers 10. At the extreme end of each armatureretainer, there is found a small housing which carries the armatureloading spring 11 (as shown by the dotted line) and a coil 19 is placedaround the core 16.

Referring to FIG. 3, a side cutout view of the matrix print head isshown.

The wire guide assembly 1 is shown having an input end 21 (whichconstitutes the cylindrical circular block at the input end) and aplanar output end 18 having a scalloped ruby 23 through which pass thestylus wires 13. The stylus wires 13 are flexibly supported by a crossbrace with an aperture and designated as the lower wire support 2.Likewise, an upper wire support 3 is also provided.

At the extreme top end of the wire guide assembly 1, there will be founda series of apertured extensions, designated as 22, which receive thestylus wire, such as 13, and act as a guide and support factor.

The stylus wire 13 has at its extreme top a nylon plastic impact buttonwhich receives the impact from armature 9 and which is rigidly andfixably attached to the stylus to carry the motion of the armature tothe wire stylus. Between the impact button 8 and the apertured extension22, there resides a wire return spring 7. This is a compression springwhich acts to cause the wire stylus 13 to return to its normal home orrest position after activation by the hammering impact of the armature9.

Also seen in FIG. 3 is the mounting means by which the wire guideassembly 1 is mounted to the mounting plate 6. This is accomplished bymounting screw 5 which connects the wire quide assembly to the mountingplate.

In FIG. 3, on the left side of the mounting plate 6, there is seen theelectromagnet assembly consisting of magnetic core 16, a magnetic yoke15, a mounting nut 17 for holding the core to the mounting plate 6, anelectric coil 19 placed around the core 16, and an armature 9 which isheld in place and retained by armature retainer 10. The armatureretainer 10 is adjustably attached to the yoke 15 by means of screw 12and mounting clamp 14. At the outward portion of the armature retainer10, there is seen a loading spring 11 which serves as an armatureloading spring to maintain the armature in a set position when themagnetic coil is de-energized.

FIGS. 4A, 4B, and 4C show in greater detail the advantageousconfiguration of the styli (at the impact receiving or input end) andthe efficacious means by which the wire styli are conveyed to the outputend in the form of a straight line configuration.

FIG. 4A shows the wire guide assembly 1 having an output end 18 whereinthe wire styli are brought into an aligned configuration by beingmounted through the center of a bearing means. The outer end of the wireguide assembly 1 is shown at 21 as the circular cylindrical block havinga configuration of apertured extensions 22. A typical aperturedextension 22 is shown guiding a wire stylus 13c, up to an impact button8. Between apertured extension 22 and the impact button 8 is acompression or return spring 7 as previously described.

FIG. 4B shows a top view of the circular cylindrical head 21 and theraised apertures 22. It will be seen that while the cylindrical block 21has a circular plane surface, the actual position of the aperturedextensions 22 are placed such that the locus of centers of the holes ofthe apertured extensions are resident along the path of an ellipse 28.

FIG. 4C shows in enlarged detail the format by which the aperturedextensions 22 on the face of the cylindrical block 21 are placed inorder to provide a locus of apertured centers 22a. It is seen thatlocations ₁ through a₉ are spotted on the major axis of the ellipse.These locations a₁ -a₉ determine the position at the output end tips 18of the nine-wire styli as they are held in the bearing means 23 (FIG.3).

The enlarged views of FIG. 4B and FIG. 4C show the placement of the holecenters 22a of the apertured extensions as lying on the periphery of anellipse. The centers of stylus tips which are marked a₁ through a₁represent the output end tips of the wire styli at the output plane 18.Taking a top view of the mechanism as looking down above over the FIG.4A, then by observing FIG. 4C, the aperture points a₁ through a₉represent the straight line which is the locus of centers of thenine-wire styli. The center holes of the apertured extension 22 areshown in FIG. 4C as 22a. The distance between any two adjacent apertures22a of the apertured extensions 22 will be found to be equal as onetravels around the periphery of the ellipse which is the locus of holecenters of the apertured extension 22. Likewise, the distance from anygiven stylus tip such as a₁ or a₂ over to the top plane of its apertureextensions 22 will also be found to be the same for each distance d₁,d₂, d₃, etc. Thus, the distance d₁ is the same as d₂, is the same as d₃,etc., is the same as d₉. It is in this manner that the overall length ofthe wire styli may be easily and efficiently made and fabricated to theexact same length.

The apparatus of the instant invention is constructed so as to be ofrugged, durable, long-wearing construction while, at the same time,being of minimal size and mass in order to facilitate the movement notonly of the wire styli and the armature hammers, but also the entireassembly into an easily accelerated condition from any static condition.

Thus, typically illustrative of an embodiment of the present inventionis the feature where the wire styli such as 13_(a), 13_(b), 13_(c), etc.are composed of wire having a circular diameter of 0.014 of an inch andhaving an elongated length of 2.52 inches from the output end tip to theinput end tip.

The armature 9 is preferably made of magnetic material such asnickel-plated steel, for example, having a thickness of 0.035 to 0.036of an inch, said armature being held in place or mounted within aplastic armature retainer 10. The magnet core 16 is typically onlyapproximately 1/ 10th of an inch in diameter and made of 21/2% siliconiron. The major usable length of the magnet core is approximately 0.65inch.

The wire guide and holder assembly 1 is made of strong but light plasticmaterial, such as Delrin AF. In addition to the apertured extension 22which positions the wire stylus at the impact receiving end, there arealso two wire guide supports, an upper wire guide support 3, and a lowerwire guide support 2 (FIG. 3). A tapered hole 3' and a tapered hole 2'are respectively placed in the upper and lower wire guide supports formaintaining the stylus in practically a straight line from the impactbutton 8 to the end or tip of the stylus at the output end 18.

The same features are true for each of the other eight styli, that is tosay, that the upper wire guide support 3 and the lower wire guidesupport 2 are provided with suitable tapered apertures or openings whichguide each individual wire stylus in a straight line to the terminationpoint at the output end 18.

At the output end 18, there is inserted a bearing 23 which receives andaligns the plurality of wire styli into a straight line such that thetip of the wire styli will lie in a flat plane. This is of course onlytrue when the styli are in their rest position, as they will extend uponactivation according to the stroke adjustment of the armature hammerwhich may drive them.

The yoke 15 of the electromagnet may be made of steel plus 1% siliconiron and may have a thickness of 0.059 inch or approximately 16 gauge.The mounting plate 6 for the print head may be made of aluminum materialapproximately 1/10th inch thick.

The coil 19 which is placed around the core 16, after having beenmounted on a nylon bobbin, may be composed of 200 turns of No. 28 wireand having a resistance of 0.95 ohms at room temperature.

Because of the simplicity of parts and assemblies of the subjectmechanism, it is an easy task to replace the armature 9 which isnormally of 20 gauge nickel-plated steel and increase its mass by, forexample, making it of 10 gauge nickel-plated steel.

OPERATION

As can be seen from FIGS. 1 and 2, upon energization of any selectedelectromagnet or group of electromagnets, the respective armatures areenergized so that they act as a hammer or deliver a sudden impact orimpulse to the impact button or impact head of the respective wirestyli.

At the output end of the print head, that is to say, the end from whichthe wire stylus projects in order to deliver an impact to an inkingribbon and record medium (such as paper) there are different situationswhich occur and which can be provided for as to the amount of travel orextension that is made by the wire styli. To a great extent, the amountof flight distance made by the wire styli would be adjusted independency upon the thickness of the inking ribbon and the thickness andtype of the, for example, paper recording medium.

Very often in these applications, it is both desirable that a multipleseries of forms be placed below the inking ribbon in order that manycopies may be printed at once. In such a case, the stroke and "flightlength" will be much less for a recording medium which has a ratherlarge thickness as, for example, a six-part printed form with carbonpaper interleaved between the forms.

On the other hand, if there is merely the printing of a single form or asingle sheet through a nylon inking ribbon, then it is necessary thatthe length of the stroke or the "flight length" be considerably longerin order to reach and print upon the single sheet or single form uponwhich the information or characters are to be printed.

Reference to FIG. 5 will illustrate the cycle time differences forimprinting a single sheet or multiple copies which are supported by aplaten 24 which is 0.030 inch from the output plane 18.

As an example of the present configuration and taking the situationwherein a single sheet or one part form is used which has, sayapproximately, a thickness of 0.003 inch, and where under this situationthe single sheet of paper or recording medium is supported by a platen24 which is 0.030 inch in distance from the output plane 18 of thematrix print head, then, under these conditions, the flight length ofthe output edge or tip of the wire styli is of the order of 0.025 inch,since the width of the recording medium which is 0.003 inch and thewidth of the nylon ribbon which is 0.003 inch shortens the distancebetween the output plane 18 of the print head and the ribbon line abovethe platen. Thus, the flight length or wire motion of 0.025 inch willensure that there is a penetration of the nylon ribbon by at least 0.001inch which is sufficient to properly cause an imprintation on the paperrecord medium.

In the apparatus of the present invention, when current is applied to aselected electromagnet or selected group of electromagnets in order toactivate the respective styli, there may be a period of approximately200 microseconds for the current to rise from zero to the required 4amperes. This energization of the electromagnetic coil activates themagnetic armature into motion in order that it may act as a hammer anddeliver a sudden impact to the impact button or impact head of therespective wire styli. From initiation of impact by the armature hammeragainst the impact heads, there is an acceleration provided to the wirestylus causing it to fly toward the nylon ribbon and record medium. Thearmature hammer may remain in contact with the impact head in a drivingmotion for approximately 200 to 250 microseconds as shown at line 25,after which the wire stylus continues to fly alone toward the nylonribbon and record medium for approximately 300 microseconds at whichtime the impact of the nylon ribbon occurs.

Then, under the influence of the bias spring 7, the wire stylus isimpelled back toward its home position and may take approximately 400microseconds to return to home position. Before the wire stylus comes torest, there may be a slight overshoot and return to rest which occurswithin a period of 100 microseconds.

Thus, from the initial moment of impact and acceleration of motion ofthe wire stylus from its home position to impact with the nylon ribbonand then return to the home position in a rest position, there will havetaken approximately 1,000 microseconds.

Thus, due to the situation of using a platen separated by 0.030 from theplane of the output end of the print head, and using a single sheetpaper of say, approximately, 0.003 inch and a nylon inking ribbon of0.003 it will be seen that it is possible to achieve a speed of dotprinting of 1,000 imprintations per second, that is to say, as the headis moved across the paper record medium, it may print 1,000 dotcombinations across the record medium per second as the head movesacross the record medium (or as the paper is moved past the print head).

Now looking at the situation where the printer head is used to printupon mulitple copies such as, for example, a six-part form having atotal thickness of 0.018 inch, if the distance from the output plane 18of the print head to the underlying platen is again a total of 0.030inch and the six-part form consumes 0.018 inch and a nylon ribbon fillsup 0.003 inch, we then see that there is left remaining a distance of0.030 less 0.021 or equal to 0.009 inch spacing or distance between thenylon ribbon and the output plane of the print head.

In this situation, again assuming a 200 microsecond period to achievecomplete energization of the electromagnet, the flight length will beonly approximately 0.009 inch plus 0.001 inch penetration into the nylonribbon for a total of 0.010 inch flight length, that is to say, flightlength from rest position to impact against the nylon ribbon forimprintation upon the record medium.

In this particular case, due to the shorter flight length, theaccelerating wire stylus (having only 0.010 inch flight length) willachieve its impact within 200 to 250 microseconds after which, thespring biasing means will cause the wire stylus to return to homeposition within 200 microseconds, and then will require approximatelyanother 200 microseconds to stabilize at rest in the home position.Thus, in this case, using the multiple copy forms and a shorter flightlength, the entire initiation, impact and return-to-rest cycle has takenonly 800 microseconds. Thus, in this case with the multiple copy formsand shorter flight time, the actual printing speed is even higher thanin the previous case. Thus, in the case at hand, it would be possible toimprint 1,250 dot imprintations per second either by motion of the printhead across the paper or motion of the paper across the print head.

Assuming a character imprintation system wherein characters are printedout by means of the matrix print head, and each character is composed ofa block or matrix which may be 9 dots high and 4 dots wide, and furtherassuming the space between any two given letter characters as being one"blank", it would then take 5 dot sequences to constitute one characterspace (including the character imprintation and its space to the nextcharacter).

Taking this figure of 5 and dividing this into the figure of 1,250, then250 characters per second could be printed by the machine which uses thepresently developed wire matrix print head.

Reliability tests on the print head of the present invention havealready indicated more than 200,000,000 successive operations withoutfailure or inadequacy or operation. This is quite remarkable consideringthat the cost and simplicity factor has been reduced by at least afactor of 5 to 10 over previously known print heads.

Having thus described and illustrated the elements of this wire matrixprinter, the following claims are made.

I claim as my invention:
 1. A wire matrix impact print head comprising amounting plate;stylus guide means affixed to said plate; a plurality ofelectromagnetic structures mounted to said plate and disposed aroundsaid guide means, each of said electromagnetic structures having anouter pole, a center pole coupled to said outer pole, and a coildisposed around one of said poles; a plurality of armatures disposedradially about said guide means, each of said armatures being associatedwith one of said electromagnetic structures to form an electromechanicalactuator for transferring electromechanical energy to a stylus, and eachof said armatures having a stylus engaging end and an outer end thatextends in cantilevered fashion outside of said outer pole; a pluralityof styli carried by said guide means, each of said styli being of anelongated rod-like configuration having a free head end for engagementby the stylus engaging end of one of said armatures and a printing endfor impacting a recording medium when the stylus is propelled throughsaid guide means by one of said actuators; each stylus of said pluralityof styli has a length and mass equal to the length and mass of each ofthe other styli being held by said guide means for substantiallystraight line movement; said guide means is so formed as to position thelocus of the free head ends of the styli on the periphery of an ellipse;a plurality of retaining means each having a central portion connectedto said guide means; and an arm engaging the outer end of one of saidarmatures for applying a moment of force thereto tending to cause thestylus engaging end to rotate about said outer pole toward said centralportion.
 2. A wire matrix impact print head comprising:a mounting platehaving a central aperture; a guide connected to said mounting plate andextending through said central aperture, the top end of said guidehaving a plurality of guide apertures arranged in an elliptical array,and the bottom end of said guide having a plurality of guide aperturesarranged in a straight line array; a plurality of springs; a pluralityof styli, each having an enlarged head at one free end and passingthrough one of said springs, through one of said guide apertures in saidtop end of said guide and through one of said guide apertures in saidbottom end of said guide, said springs serving to resiliently bias saidstyli into a rest position; a plurality of electromagnetic structuresconnected to said mounting plate, each of said structures having anouter pole, a center pole coupled to said outer pole, and a coil mountedaround one of said poles; a plurality of elongated armatures each havinga stylus engaging end and an outer end, and each being associated withone of said electromagnetic structures and pivotable about the outerpole thereof; the respective combinations of armature andelectromagnetic structure forming a plurality of electromagneticactuators for selectively propelling various ones of said styli throughsaid guide apertures; and a plurality of retainers coupled to saidmounting plate and each including a central portion having a shockabsorbing means and an arm radiating from said central portion, each ofsaid arms (1) engaging one of said outer ends to hold the associatedarmature in contact with one of said outer poles to form anelectromagnetic actuator, (2) holding the associated armature inalignment with one of said heads of one of said styli, and (3) providinga moment of force to the associated armature tending to cause thearmature to rotate about the associated outer pole and into engagementwith said shock absorbing means, said retainer further including anadjustment means for enabling the air gaps between the armatures and thecenter poles of each of said electromagnetic actuators to be adjusted.3. A wire matrix printing head comprising a plurality of wire styli eachof which has a free input end and a free output end, bearing meansforced with a planar recording medium accomodating surface and bearingapertures for constraining said styli output ends each substantiallyperpendicular to said planar recording medium accomodating surface, eachof said wire styli being of equal length and mass, guide means forconstraining the input ends of such styli relatively to the output endsthereof such that the projection of each equal length styli on theplanar recording medium accomodating surface is a line of equal length,and a plurality of electromagnetic activation means carried by saidguide means and associated one with each one of said wire styli, each ofsaid electromagnetic activation means including an armature separatefrom said associated stylus, pivotal support means for said armature, anelectromagnetized core for driving said armature about said pivotalsupport means, and means for constraining each armature substantiallyperpendicular to said associated stylus and with a portion of saidarmature arranged for driving engagement with the free input endthereof, the armatures and electromagnetized cores for each of saidelectromagnetic activation devices being identical to each other andarranged each with equal distances between said pivotal support meansand said electromagnetized cores and between said pivotal support meansand the portion arranged for driving engagement with said associatedstylus input end.
 4. A wire matrix printing head as set forth in claim 3wherein each of said armature portions arranged for driving engagementwith the associated stylus is tapered in width a substantially equalamount and wherein said armature portions which are arranged for drivingengagement with the associated styli are disposed relatively to eachother in evenly spaced relation with minimum uniform spacingtherebetween only sufficient for accomodation of independent armatureactivation without interference thus to provide for the shortest equalprojected length of each of said styli on the planar recording mediumaccomodating surface.